Animals that live at high altitude have evolved a number of physiological adaptations to deal with the low atmospheric oxygen concentrations (hypoxia). For low altitude acclimated animals, short exposures to high altitude results in activation of the sympathetic nervous system (i.e. the fight or flight response). This is a good thing because activation of this system results in more blood flow, especially to the heart and brain to help protect oxygen delivery to these vital tissues. Chronic activation of the system, however, can lead to cardiovascular diseases and other stress-related disorders.
To examine how altitude affects physiology, it makes sense to find and compare populations of animals living at low vs high altitude. In a new study published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, researchers did just that. They compared populations of North American deer mice (Peromyscus maniculatus) that were native to either low (lowland) or high (highland) altitudes. They raised offspring of these populations at sea level then examined changes that took place when exposed to high altitude. What they found was that highland mice acclimated to hypoxia had less activation of the sympathetic nervous system and smaller adrenal glands (i.e. lower stress hormones) than lowland mice exposed to hypoxia. These changes are likely genetic in nature and may help the mice live at high altitude by preventing chronic stress and the negative health effects that can come along with it.
AL Scott, NA Pranckevicius, CA Nurse, GR Scott. Regulation of catecholamine release from the adrenal medulla is altered in deer mice (Peromyscus maniculatus) native to high altitudes. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology. 317(3): R407-417, 2019. https://doi-org.ezproxy1.lib.asu.edu/10.1152/ajpregu.00005.2019